Light-guiding device, virtual image display apparatus, and method for manufacturing light-guiding device

ABSTRACT

A light-guiding device includes a pair of light-guiding portions, a pair of light-incident portions that causes image light to be incident on the pair of light-guiding portions respectively, and a pair of light-emitting portions that emit image light, guided by the pair of light-guiding portions, to outside respectively, in which a pair of optical members including the pair of light-guiding portions are coupled by a central member having light transmissivity, and separate overcoat layers are provided at the optical member on one side and at the optical member on another side with respect to an approximate center of the central member.

The present application is based on, and claims priority from JPApplication Serial Number 2018-224621, filed Nov. 30, 2018, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a virtual image display apparatus anda method for manufacturing a light-guiding device that present a virtualimage to an observer, and particularly relates to a light-guiding devicethat enables see-through viewing.

2. Related Art

As a light-guiding device that enables see-through viewing, a device isknown which includes a pair of light-guiding members each provided witha light-guiding portion, a light-incident portion, and a light-emittingportion, where the right and left light-guiding members are coupled by alight transmission member located at the center to configure a singlelight-guiding device (FIG. 10 of JP 2017-111363 A). Note that, as amethod for manufacturing the light-guiding device, a hard coat layer mayoccasionally be formed by dip processing on a surface of a resin basematerial.

However, in a structure in which the right and left light-guidingmembers are coupled by the light transmission member located at thecenter as in JP 2017-111363 A, there are several issues to be resolvedat the time when forming of the hard coat layer. That is, whenattempting to form a hard coat layer with the resin base material beingin a landscape-oriented state, the surface when leaving the liquidbecomes larger, causing an occurrence of liquid pooling at theunderportion to lead to a whitening with high probability, and the poorappearance results in a decrease in yield. On the other hand, whenattempting to form the hard coat layer with the resin base materialbeing in a portrait-oriented state, causing a concentration of the hardcoat liquid at the throttle portion to lead to an occurrence of saggingnear the center portion, and resulting in poor appearance and a decreasein yield. In addition, when steps are provided at the light-guidingmember or the like, the orientation of a pair of corresponding steps isreversed in a pair of light-guiding members due to the shape symmetry ofthe light-guiding device when pulling up the light-guiding members froma coating solution, causing a whitening of the hard coat layer or anincrease of non-uniformity in thickness, around the step of either oneof the light-guiding members.

SUMMARY

A light-guiding device according to an aspect of the present disclosureis the light-guiding device including a pair of light-guiding portions,a pair of light-incident portions configured to cause image light to beincident on the pair of light-guiding portions respectively, and a pairof light-emitting portions configured to emit image light, guided by thepair of light-guiding portions, to outside respectively, in which a pairof optical members including the pair of light-guiding portions arecoupled by a central member, and separate overcoat layers are providedat the optical member on one side and at the optical member on anotherside with respect to an approximate center of the central member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory cross-sectional view illustrating a virtualimage display apparatus including a light-guiding device according to afirst embodiment.

FIG. 2 is a front view of a light-guiding device.

FIG. 3 is a plan view of a light-guiding device.

FIG. 4 is an explanatory plan cross-sectional view conceptuallyillustrating a structure of a display device on one side and an opticalpath of video light.

FIG. 5A is an explanatory front view partially illustrating a structureof a central member of a see-through light-guiding unit.

FIG. 5B is an explanatory front view partially illustrating a shape of acentral member of a see-through light-guiding unit.

FIG. 6 is an explanatory plan view illustrating a range in which anovercoat layer is formed.

FIG. 7 is an explanatory perspective view conceptually illustrating amethod of forming an overcoat layer.

FIG. 8 is an explanatory view illustrating a forming process of anovercoat layer.

FIG. 9 is an explanatory view illustrating a forming process of anovercoat layer.

FIG. 10 is an explanatory front view partially illustrating alight-guiding device according to a second embodiment.

FIG. 11 is an explanatory front view partially illustrating alight-guiding device according to a third embodiment.

FIG. 12 is an explanatory plan view illustrating a light-guiding deviceaccording to a fourth embodiment.

FIG. 13 is an explanatory graph illustrating thickness of an overcoatlayer.

FIG. 14 is an explanatory front view partially illustrating alight-guiding device according to a fifth embodiment.

FIG. 15 is an explanatory view illustrating a modification of thelight-guiding device illustrated in FIG. 14.

FIG. 16 is an explanatory front view partially illustrating alight-guiding device according to a sixth embodiment.

FIG. 17 is an explanatory front view partially illustrating alight-guiding device according to a seventh embodiment.

FIG. 18 is an explanatory front view partially illustrating alight-guiding device according to a seventh embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

Hereinafter, a virtual image display apparatus according to a firstembodiment of the present disclosure will be described below withreference to FIG. 1 and the like.

As illustrated in FIG. 1, a virtual image display apparatus 100according to the first embodiment, which is a head-mounted display (HMD)having an eyeglass-like appearance, can allow an observer or userwearing the virtual image display apparatus 100 to visually recognizeimage light or video light due to virtual image, as well as can allowthe observer to observe an external image in a see-through manner. Thevirtual image display apparatus 100 includes a first display device 100Aand a second display device 100B. In FIG. 1, X, Y, and Z are anorthogonal coordinate system, where the ±X directions correspond to alateral direction in which both eyes of an observer wearing the virtualimage display apparatus 100 are aligned, the Y direction corresponds toa downward direction orthogonal to the lateral direction in which theboth eyes of the observer are aligned, and the Z direction correspondsto a front direction or a front surface direction of the observer.

The first display device 100A and the second display device 100B areparts that form a virtual image for the right eye and a virtual imagefor the left eye, respectively. The first display device 100A for theright eye includes a first virtual image forming optical portion 101 athat covers the front of an eye of the observer in a see-through manner,and a first image forming body 105 a that generates image light. Thesecond display device 100B for the left eye includes a second virtualimage forming optical portion 101 b that covers the front of an eye ofthe observer in a see-through manner, and a second image forming body105 b that generates image light. The first and second image formingbodies 105 a and 105 b are each constituted by optical elements (notillustrated) such as a video forming device, a projection lens, and thelike, and a member that houses these optical elements, and the like.Note that the optical elements in the first and second image formingbodies 105 a and 105 b are covered by case members 105 d in a cover-likeform and supported within the case members 105 d. The first and secondvirtual image forming optical portions 101 a and 101 b each cause imagelight generated by the first and second image forming bodies 105 a and105 b to be guided and superimposes the external light with the imagelight to be visually recognized. The first and second virtual imageforming optical portions 101 a and 101 b form a see-throughlight-guiding unit 100C being a unitary member coupled together at thecenter rather than separate members. The see-through light-guiding unit100C, which is a light-guiding device 20 of a composite type thatprovides visual images for both eyes to an observer by means of guidedlight, is supported by the case members 105 d in a cover-like form atthe both ends.

The first and second image forming bodies 105 a and 105 b are attachedwith temples 104 being trailing portions extending rearward at the rearportions pivotally by non-illustrated hinges, where the temples 104function as support portions that are caused to abut against the ears,temple, and the like of an observer to ensure a wearing state. A centercover 100D covering the center portion of the see-through light-guidingunit 100C is fixed between the first and second virtual image formingoptical portions 101 a and 101 b, that is, at the center in the ±Xdirections of the see-through light-guiding unit 100C. The center cover100D supports a pair of nose pads 106 and 106. The nose pads 106 and106, which constitute the support portions together with the temples104, are caused to abut against the nose of the observer to enablepositioning of the see-through light-guiding unit 100C and the likerelative to the eyes of the observer.

A structure of the see-through light-guiding unit 100C, that is, thelight-guiding device 20 will be described below with reference to FIGS.2 and 3.

The see-through light-guiding unit 100C includes a pair of light-guidingmembers 10 a and 10 b and a central member 50. The pair of light-guidingmembers 10 a and 10 b are a pair of optical members 21 a and 21 b thatcontribute to virtual image formation along with propagating image lightinside therethrough. The pair of light-guiding members 10 a and 10 b,that are, the pair of optical members 21 a and 21 b, are fixed to therespective both ends of the central member 50. The see-throughlight-guiding unit 100C is provided in a straight line-like or rod-likeform, as a whole. The see-through light-guiding unit 100C being within ahorizontal XZ plane, while protruding forward with slightly bent at thecenter of the central member 50, has a symmetrical shape. Thelight-guiding members 10 a and 10 b have center axes CX1 and CX2 thatform an angle θ relative to a center axis CX3 of the central member 50.

The optical member 21 a being the light-guiding member 10 a on one hand,which is provided with a light-incident portion 20 a at the end portionon the +X side and a light-emitting portion 20 b at the end portion onthe −X side, includes a structure in which a light-guiding portion 20 cextends between the light-incident portion 20 a and the light-emittingportion 20 b, where the light guiding direction as a whole is adirection approximating the −X direction, and is slightly inclined inthe +Z direction. The light-guiding member 10 a on one hand is anintegrated member, but can be recognized as separated into a first lightguiding part 11 on the light exiting side and a second light guidingpart 12 on the light incident side. The first light guiding part 11 ofthe light-guiding member 10 a is provided with a first face S11 being aflat plane facing an eye of the observer, and a second face S12 being acurved plane inclined relative to the first face S11 at the boundarywith the central member 50, and is provided with a third face S13 beinga flat plane facing the first face S11 and extending parallel thereto.The second light guiding part 12 of the light-guiding member 10 a isprovided with a fourth face S14 being a curved plane facing the thirdface S13, and a fifth face S15 being a curved plane inclined relative tothe fourth face S14. The fifth face S15, which is a plane beingnon-transmissive of light, is provided with a reflective film RM. In thefirst light guiding part 11, a half mirror 15 is collaterally providedon the surface of the second face S12 facing the central member 50. Thehalf mirror 15 is a reflective film having light transmissivity (thatis, a semi-transmission reflective film), which is formed by filmforming a metallic reflective film or a dielectric multilayer film, andis appropriately set with a reflectivity with respect to the imagelight. In the first light guiding part 11 of the light-guiding member 10a, a lower surface 10 u and an upper surface 10 t are flat planes beinghorizontal and parallel to each other, which extend along the XZ plane.The lower surface 10 u and the upper surface 10 t are not required to beexactly parallel to the XZ plane, and may have slight inclination orunevenness within a range that does not interfere with an optical pathof image light or the like. The light-guiding member 10 b or the opticalmember 21 b on the other hand, which is laterally inverted with respectto the light-guiding member 10 a or the optical member 21 a on one hand,has a structure and shape as in the light-guiding member 10 a or theoptical member 21 a on one hand. Thus, the redundant descriptionsthereof will be omitted, denoting the same portions by the samereference signs as in the light-guiding member 10 a or the opticalmember 21 a on one hand.

A pair of fastening portions 12 f and 12 g provided on the upper surfaceand the lower surface at the side of the light-incident portions 20 adisposed on outer end portions of the optical members 21 a and 21 bserve as parts for aligning and fixing the image forming bodies 105 aand 105 b with respect to the light-incident portions 20 a.

The central member 50 having light transmissivity includes a pair oflight transmissive portions 50 a and 50 b, and a coupling portion 50 d.At the light transmissive portion 50 a on one hand, a first transmissionface S51 being a flat plane facing an eye of the observer is provided,and a third transmission face S53 being a flat plane facing the firsttransmission face S51 and extending parallel thereto is provided. Asecond transmission face S52 is disposed between the first transmissionface S51 and the third transmission face S53. The first transmissionface S51 is on a face extended from the first face S11 of thelight-guiding member 10 a on one hand, the second transmission face S52is a curved plane being joined to and integrated with the second faceS12 of the light-guiding member 10 a on one hand, and the thirdtransmission face S53 is on a face extended from the third face S13 ofthe light-guiding member 10 a on one hand. In other words, the firstface S11 and the first transmission face S51 are adjacent to each other,and similarly, the third face S13 and the third transmission face S53are adjacent to each other, where the respective surfaces are in analigned state flush with each other to form smooth surfaces. In thelight transmissive portion 50 a, a lower surface 50 u and an uppersurface 50 t are flat planes being horizontal and parallel to eachother, which extend along the XZ plane. The lower surface 50 u of thelight transmissive portion 50 a is disposed parallel to andsubstantially flush with the lower surface 10 u of the light-guidingmember 10 a. The upper surface 50 t of the light transmissive portion 50a is disposed parallel to and flush with the upper surface 10 t of thelight-guiding member 10 a. That is, a part at which the lighttransmissive portion 50 a is coupled to the first light guiding part 11of the light-guiding member 10 a and a periphery of the part have arectangular cross-section at each of the positions along the center axisCX1. The lower surface 50 u and the upper surface 50 t are not requiredto be exactly parallel to the XZ plane, and may have slight inclinationor unevenness within a range that does not interfere with an opticalpath of external light. The light transmissive portion 50 b on the otherhand, which is laterally inverted with respect to the light transmissiveportion 50 a on one hand, includes a structure as in the lighttransmissive portion 50 a on the other hand. Thus, the redundantdescriptions thereof will be omitted, denoting the same portions by thesame reference signs as in the light transmissive portion 50 a on onehand. The coupling portion 50 d, which includes a portion bent in abridge shape, includes a notch 57 recessed upward from the lower surface50 u relative to the light transmissive portion 50 a and 50 b, andincludes a protrusion portion 58 that protrudes at the upper side of theupper surface 50 t relative to the light transmissive portions 50 a and50 b. That is, a lower surface 50 q of the coupling portion 50 d isdisposed at the upper side or the −Y side of the lower surface 50 u ofthe light transmissive portion 50 a and the lower surface 10 u of thelight-guiding member 10 a, and an upper surface 50 p of the couplingportion 50 d is disposed at the upper side or the −Y side of the uppersurface 50 t of the light transmissive portion 50 a and the uppersurface 10 t of the light-guiding member 10 a. A provision of a notch 57having a depth not less than a predetermined depth not only ensures aspace in which the nose is to be disposed, but also prevents image lightfrom the light-guiding member 10 a of the first virtual image formingoptical portion 101 a from being incident on the light-guiding member 10b of the second virtual image forming optical portion 101 b through thecoupling portion 50 d, or vice versa. In addition, the protrusion amountof the protrusion portion 58 is made sufficiently large, to thus preventthe coupling portion 50 d from becoming thinner to lower the strength.

A protrusion portion 50 f provided at the upper side of the centerportion (corresponding to a lateral middle portion 50 j illustrated inFIG. 5) of the coupling portion 50 d forms a positioning structure 71that aligns and fixes the center cover 100D illustrated in FIG. 1. Inthe positioning structure 71, positioning locations 71 a are provided atboth ends of the lateral direction. A gate may be provided on the topsurface of the protrusion portion 50 f when molding the central member50.

FIG. 4 is a view partially illustrating the first display device 100A,which specifically extracts a part of the optical system. As alreadydescribed above, the virtual image display apparatus 100 is constitutedby the first display device 100A and the second display device 100B (seeFIG. 1), where the first display device 100A and the second displaydevice 100B have right-left symmetrical and mutually equivalentstructures, thus the first display device 100A will be exclusivelydescribed, and the first display device 100A will be omitted to bedescribed. Note that in FIG. 4, x, y, and z form orthogonal coordinatesystem, the x and y directions are parallel to the first face S11 andthird face S13, and the z direction is perpendicular to the first faceS11 and third face S13.

The first display device 100A includes, as the image forming body 105 a,an image forming device 80 that generates image light, and a projectionlens 30 for imaging.

The image forming device 80 is a self-luminous display element typifiedby, for example, an organic electro-luminescence (organic EL), aninorganic EL, an LED array, an organic LED, a laser array, a quantum dotemission type element, and the like, and forms a still image or a videoimage in color on a display region 80 a of two-dimensional. The imageforming device 80 is driven by a non-illustrated drive control circuitto perform a display operation. When an organic EL display is used asthe image forming device 80, the image forming device 80 is configuredto include an organic EL control unit. When a quantum dot display isused as the image forming device 80, the image forming device 80 isconfigured to emit green or red color by causing light of a blue lightemitting diode (LED) to pass through a quantum dot film. The imageforming device 80 is not limited to a self-luminous display element, andmay be constituted by a light modulating element such as an LCD, and mayform an image by illuminating the light modulating element with a lightsource such as a backlight. As the image forming device 80, a liquidcrystal on silicon (LCO; LCoS is a trade name), a digital micromirrordevice, and the like may be used in place of the LCD.

The projection lens 30 protrudes the image light generated by the imageforming device 80 toward the light-guiding member 10 a of the firstvirtual image forming optical portion 101 a, and causes the image lightto be incident on the light-incident portion 20 a. The projection lens30 is a projection optical system including, as components, one or moreoptical elements or lenses aligned along a direction in which anincident-side optical axis AX extends. The optical elements thatconstitute the projection lens 30 are held by a non-illustrated lensbarrel, which is housed and supported by the case member 105 d (see FIG.1). Note that the optical elements constituting the projection lens 30can be constituted by aspherical lenses including both an asphericalsurface being non-axisymmetric and an aspherical surface beingaxisymmetric, for example. Then, the optical elements can allow anintermediate image corresponding to a displayed image on the displayregion 80 a to be formed inside the light-guiding member 10 a incooperation with the optical surface or the reflective surface of thelight-guiding member 10 a.

The light-guiding member 10 a in the first virtual image forming opticalportion 101 a is joined to the light transmissive portion 50 a via anadhesive layer CC, where the adhesive layer CC and a joining surfacebetween the light-guiding member 10 a and the light transmissive portion50 a interpose the adhesive layer CC are referred to as joining portionCN. The light-guiding member 10 a and the light transmissive portion 50a have a structure in which surfaces of body members 10 s and 50 s arecovered with an overcoat layer 27. The overcoat layer 27 is specificallya hard coat layer, and functions as a protective layer that suppressesscratching and the like of surface portions exposed at the first virtualimage forming optical portion 101 a.

The body member 10 s in the light-guiding member 10 a is composed of aresin material having high light transmissivity in the visible range,and is molded, for example, by pouring a thermoplastic resin into a moldand curing the resin. Note that a cycloolefin polymer or the like can beused as the material of the body member 10 s. The same as above alsoapplies to the light transmissive portion 50 a, and the body member 50 sis composed of the same material as the body member 10 s of thelight-guiding member 10 a. The overcoat layer 27 is produced, using amaterial having visible light transmissivity, such as a silicone-basedhard coat material, through processes of applying, drying, and curingsuch a coating material.

Hereinafter, the optical path of the image light (referred to as imagelight GL herein) will be briefly described below. The light-guidingmember 10 a allows the image light GL to be incident from the projectionlens 30 and guides the image light GL toward an eye of the observer by areflection at the first to fifth faces S11 to S15. Specifically, theimage light GL from the projection lens 30 is firstly incident on a partof the fourth face S14 provided at the light-incident portion 20 a, tothen be reflected by the fifth face S15. Then, the image light GLre-enters the fourth face S14 from inside to be totally reflected,enters the third face S13 to be totally reflected, and is then incidenton the first face S11 to be totally reflected. The image light GLtotally reflected by the first face S11 is incident on the second faceS12 and is partially reflected by the half mirror 15 provided at thesecond face S12 while partially passing through the half mirror 15, andthen re-enters a part of the first face S11 provided at thelight-emitting portion 20 b to pass therethrough. The image light GLpassing through the first face S11 is incident, as a substantiallyparallel luminous flux, on an exit pupil EP where an eye of the observeris disposed. That is, the observer is to observe an image by image lightas a virtual image.

The first virtual image forming optical portion 101 a is configured toallow the observer to visually recognize the image light by thelight-guiding member 10 a, and to allow the observer to observe anexternal image with little distortion by the light-guiding member 10 ain a state combined with the central member 50. Then, the third face S13and the first face S11 are flat planes that are substantially parallelto each other (the eyepiece visibility is approximately zero), to hardlycause an aberration and the like for the external light OL. Similarly,the third transmission face S53 and the first transmission face S51 areflat planes that are substantially parallel to each other as well. Inaddition, the third transmission face S53 and the first face S11 areflat planes that are substantially parallel to each other, to hardlycause an aberration and the like. As described above, the observer is toobserve a distortion-free external image through the central member 50.Note that a light guiding direction DD1 of the entirety of the luminousflux of the image light GL at the light-guiding member 10 a is adirection in which the light-guiding member 10 a and the lighttransmissive portion 50 a extend as illustrated in the figure, and thelight guiding direction DD1 is typically parallel to the center axis CX1that will be described below.

The shape of the see-through light-guiding unit 100C or the centralmember 50, particularly the shape and structure of the coupling portion50 d will be described below with reference to FIG. 5A. In thesee-through light-guiding unit 100C, the coupling portion 50 d of thecentral member 50 includes a pair of end portions 50 y coupled to theoptical members 21 a and 21 b via the light transmissive portions 50 aand 50 b, and a bridge portion 50 z extending between the pair of endportions 50 y. The bridge portion 50 z is a portion composed by theprotrusion portion 58 combined with the notch 57. The protrusion portion58 is a portion that protrudes in a trapezoidal shape with respect tothe upper surface 10 t or the upper surface 50 t, which is the upper endof the light-guiding member 10 a in a front view, and the notch 57 is aportion being recessed in a trapezoidal shape with respect to the lowersurface 10 u or the lower surface 50 u, which is the lower end of thelight-guiding member 10 a in a front view. The notch 57 is sufficient toblock a straight light path between the light-guiding members 10 a and10 b, and is recessed upward or toward the −Y direction to narrow thelight path from the lower side. The protrusion portion 58, which servesto compensate a decrease in strength of the coupling portion 50 d due tothe formation of the notch 57, bulges upward or toward the −Y direction,to suppress a decrease in thickness related to the vertical direction orthe ±Y direction of the bridge portion 50 z.

The bridge portion 50 z includes the lateral middle portion 50 j at themiddle in the lateral ±x direction as a portion interposed by the pairof end portions 50 y. That is, the lateral middle portion 50 j is a partof the coupling portion 50 d or the bridge portion 50 z. In the lateralmiddle portion 50 j, a center C3 related to the Y direction orthogonalto the light guiding direction DD1 (see FIG. 4) due to the light-guidingmembers 10 a and 10 b is disposed in a state shifted toward the −Ydirection side being upward relative to centers C1 and C2 related to theY direction of the light-guiding members 10 a and 10 b or the opticalmembers 21 a and 21 b. In the above state, the center C3 related to theY direction of the lateral middle portion 50 j is at a position throughwhich the center axis CX3 of the lateral middle portion 50 j passes. Inaddition, the center C1 related to the Y direction of the optical member21 a is at a position through which the center axis CX1 of thelight-guiding member 10 a and the like passes, and the center C2 of theoptical member 21 b related to the Y direction is at a position throughwhich the center axis CX2 of the light-guiding member 10 b passes.Although not illustrated in the figure, the center C3 of the lateralmiddle portion 50 j in the bridge portion 50 z is disposed in the −Ydirection above the upper end of the half mirror 15 or an effectiveregion of the half mirror 15, or the center C3 is disposed in the −Ydirection above the upper surface 10 t or the upper surface 50 t of theoptical member 21 a, to thus more reliably suppress the image light fromcoming and going between the pair of optical members 21 a and 21 b.Moreover, the lower surface 50 q of the lateral middle portion 50 j inthe bridge portion 50 z is disposed in the −Y direction above the upperend of the half mirror 15 or the effective region of the half mirror 15,or the lower surface 50 q is disposed in the −Y direction above theupper surface 10 t or the upper surface 50 t of the optical member 21 a,to thus enhance an effect of blocking the image light.

The shape of the coupling portion 50 d or the bridge portion 50 z willbe described below in a different view point, with reference to FIG. 5B.A coupling portion 950 d indicated by a dot-dash line represents acomparative example, which is virtual and standard, having a shape beingvertically balanced. In case of the coupling portion 950 d of thecomparative example, the coupling portion 950 d has a shape beingvertically balanced, the width related to the vertical direction or the±Y direction gradually decreases toward both ends, and the width or wallthickness in the vertical direction becomes uniform at the center. In alateral middle portion 950 j of the bridge portion 50 z, the center C0related to the −Y direction as a first direction is disposed at anidentical position related to the ±Y direction relative to the centersC1 and C2 related to the −Y direction as the first direction of theoptical members 21 a and 21 b. On the other hand, in case of thecoupling portion 50 d of the embodiment, the center C3 related to thevertical location of the lateral middle portion 50 j is disposed in astate shifted by a distance SL toward the −Y direction side being upwardrelative to the centers C1 and C2 related to the vertical location ofthe optical members 21 a and 21 b and the center C0 related to thevertical location of the lateral middle portion 950 j being verticallybalanced of the comparative example. A body part 5 a in a rod-like formconstituting the coupling portion 50 d of the embodiment has a shape andarrangement that a body part 5 x in a rod-like form constituting thecoupling portion 950 d of the comparative example is shifted toward the−Y direction side being upward. As described above, the body part 5 x isappropriately shifted toward the −Y direction side being upward, to thusform the protrusion portion 58 at the upper side, and the notch 57 atthe lower side.

The protrusion portion 58 is, but not limited to, a trapezoidal shape asillustrated in the figure, and is sufficient to have a shape that doesnot abut against between the eyebrows, and may be, for example, a thickportion that reinforces the strength of the coupling portion 50 d by anincrease of the thickness. The protrusion portion 58 may have a shapethat protrudes at two locations, for example. The notch 57 is, but notlimited to, a trapezoidal shape as illustrated in the figure, and maybe, for example, a recess such as a triangular, square, or semi-circularshape, in a front view. At the center of the notch 57, the lower surface50 q is not required to be parallel to the XZ surface, and may be asurface being inclined toward the inner side or the −Z side, forexample. When the protrusion portion 58 has a shape that protrudes attwo locations, the notch 57 may be two notched parts recessed upward atthe lower side of the two protrusion portions 58.

FIG. 6 is an explanatory view illustrating the overcoat layer 27 formedat a surface of the see-through light-guiding unit 100C or thelight-guiding device 20. The overcoat layer 27 includes, as illustratedin the figure as small dot patterned regions, a first overcoat layer 27a and a second overcoat layer 27 b, as separate overcoat layers or apair of overcoat layers covering a base material JP that should becomethe light-guiding device 20. The first overcoat layer 27 a is providedat the optical member 21 a on one side, and the second overcoat layer 27b is provided at the optical member 21 b on the other side. The firstovercoat layer 27 a and the second overcoat layer 27 b are spaced apartfrom each other at the approximate center or the center portion of thecentral member 50 (the lateral middle portion 50 j), to form an exposedregion AE. That is, the first overcoat layer 27 a on one hand isprovided at the light-guiding member 10 a constituting the first virtualimage forming optical portion 101 a and at the remaining regionexcluding the center portion of the bridge portion 50 z in the centralmember 50. The second overcoat layer 27 b on the other hand is providedat the light-guiding member 10 b constituting the second virtual imageforming optical portion 101 b and the remaining regions excluding thecenter portion of the bridge portion 50 z in the central member 50. As aresult, both the overcoat layers 27 a and 27 b are provided in a mannerto avoid the positioning locations 71 a of the positioning structure 71.This allows finishing accuracy of the positioning locations 71 a to bemaintained in a simple manner. The first overcoat layer 27 a and thesecond overcoat layer 27 b may be composed of an identical material orcomposition, or may be composed of different materials or compositions.

The see-through light-guiding unit 100C includes, at the back side onwhich the exit pupil EP is provided, an outward step SA1 in a concaveshape at a tip end side away from the central member 50, and includes,at the front side on which the external light is incident, an outwardstep SA2 in a concave shape at the tip end side away from the centralmember 50, that is at the light-incident portion 20 a side. The outwardstep SA1 on one hand is provided in the boundary region between thefirst face S11 and the fourth face S14, extends substantially along thevertical ±Y direction, and is covered by the overcoat layers 27 a and 27b. The direction in which the outward step SA1 extends is substantiallyorthogonal to the light guiding direction DD1 (see FIG. 4), and issubstantially orthogonal to a pulling-up direction DX1 (see FIG. 7) thatwill be described below, and corresponds to the vertical direction whenthe see-through light-guiding unit 100C is worn. The outward step SA2 onthe other hand is provided in the boundary region between the third faceS13 and the fifth face S15, extends substantially along the vertical ±Ydirection, and is covered by the overcoat layers 27 a and 27 b. Thedirection in which the outward step SA2 extends is substantiallyorthogonal to the light guiding direction DD1 (see FIG. 4) and thepulling-up direction DX1 (see FIG. 7), and corresponds to the verticaldirection when the see-through light-guiding unit 100C is worn.

The outward steps SA1 and SA2 provided at the light-guiding member 10 acorresponding to the right eye correspond to the first overcoat layer 27a, where when the base material JP is pulled up from a coating solutionin forming the first overcoat layer 27 a, the base material JP isfavorably moved toward the −X direction with the tip end side at whichthe light-incident portion 20 a is provided being located at the lowerside. In this case, the outward steps SA1 and SA2 are in an overhangingstate, suppressing an occurrence of a liquid pooling of the coatingsolution. Note that, contrary to the above, when the base material JP ismoved toward the +X direction with the tip end side at which thelight-incident portion 20 a is provided being located at the upper side,a large liquid pooling of the coating solution readily occurs at theoutward steps SA1 and SA2 in a shelf shape, to facilitate an occurrenceof dripping under the liquid pooling. Similarly, the outward steps SA1and SA2 provided at the light-guiding member 10 b corresponding to theleft eye correspond to the overcoat layer 27 b, where when the basematerial JP is pulled up from a coating solution in forming the overcoatlayer 27 b, the base material JP is favorably moved toward the +Xdirection with the tip end side at which the light-incident portion 20 ais provided being located at the lower side. In this case, the outwardsteps SA1 and SA2 are in an overhanging state, suppressing an occurrenceof a liquid pooling or dripping of the coating solution.

A film formation of the overcoat layer 27, which is a main part of themethod for manufacturing the light-guiding device 20, will be describedbelow with reference to FIG. 7. The base material JP is preparedbeforehand, in which the body members 10 s of the pair of opticalmembers 21 a and 21 b are joined, from the both ends, to the body member50 s of the central member 50. The base material JP is composed suchthat the half mirror 15 is embedded at the joining portion CN. Inaddition, the base material JP is provided with the reflective film RMof the fifth face S15. Note that FIG. 7 illustrates a state prior to aformation of a surface portion such as an optical surface, however, eventhe base material JP before the formation of the overcoat layer 27, forexample, is illustrated as the light-guiding device 20, for convenienceof explanation.

As illustrated in the figure, the base material JP is caused to be in astate of being fixed to and hung from a non-illustrated jig of anelevating mechanism at an attachment location JPa at one end, and aprocessing tank DT filled with a coating solution CL is prepared. Thebase material BT is moved up and down along the direction indicated byan arrow Dl while being supported by the jig of the elevating mechanism,and then, the film formations of the pair of overcoat layers 27 a and 27b constituting the overcoat layer 27 are to be sequentially performed.Note that one of the directions indicated by the arrow Dl is agravitational direction G, and corresponds to an operation of immersingthe base material JP in the coating solution CL, and the other is thepulling-up direction DX1 in which the base material JP is elevated fromthe coating solution CL against the gravitational force.

First, as indicated by a dotted line in FIG. 8, the base material JP ismoved downward in the gravitational direction G, to be brought into astate where the lower half of the base material JP is immersed in theprocessing tank DT containing the coating solution CL. Here, theprotrusion portion 50 f on the base material JP is prevented from beingimmersed in the coating solution CL. Thereafter, as indicated by a solidline in FIG. 8, the base material JP is pulled up in the pulling-updirection DX1 at a predetermined speed, to be brought into a state wherethe coating solution CL has been applied to the surface of the basematerial JP. The coating solution CL applied to the surface of the basematerial JP forms a coating film CF that covers the surface of the lowerhalf of the base material JP with substantially uniform thickness byflowing on the surface of the base material JP pursuant to thegravitational force, the viscosity and surface tension of the coatingsolution CL, and the like. Then, the coating film CF becomes thick dueto the liquid pooling of the coating solution CL at the recesses of theoutward steps SA1 and SA2, however, the liquid pooling does not becomelarge. The coating film CF on the base material JP, after being dried,is subjected to processing of ultraviolet radiation or heating to becured, forming the first overcoat layer 27 a.

Next, as indicated by a dotted line in FIG. 9, the base material JPbeing vertically inverted is moved downward in the gravitationaldirection G while being fixed to the jig at an attachment location JPbat the other end, to be brought into a state where the lower half of thebase material JP is immersed in the processing tank DT containing thecoating solution CL. Here, the protrusion portion 50 f on the basematerial JP is prevented from being immersed in the coating solution CL.Thereafter, as indicated by a solid line in FIG. 9, the base material JPis pulled up in the pulling-up direction DX1 at a predetermined speed,to be brought into a state where the coating solution CL has beenapplied to the surface of the base material JP. The coating solution CLapplied to the surface of the base material JP forms a coating film CFthat covers the surface of the lower half of the base material JP withsubstantially uniform thickness. Then, the coating film CF becomes thickdue to the liquid pooling of the coating solution CL at the recesses ofthe outward steps SA1 and SA2, however, the liquid pooling does notbecome large. The coating film CF on the base material JP, after beingdried, is subjected to processing of ultraviolet radiation or heating tobe cured, forming the first overcoat layer 27 b.

Although descriptions are omitted above, a local polishing on thejoining portion CN of the base material JP may be performed as apreprocessing prior to the film formation of the overcoat layer 27. Inaddition, as the preprocessing prior to the film formation of theovercoat layer 27, an underlayer film for embedding and smoothing theprocessing marks formed at the surface of the base material JP may alsobe formed.

In the light-guiding device 20 of the first embodiment, separate hardcoat layers 27 a and 27 b provided at the optical member 21 a on oneside and the optical member 21 b on the other side relative to theapproximate center of the central member 50 enables manufacturing thehard coat layers 27 a and 27 b of the pair of optical members 21 a and21 b in symmetrical processes, and thus the liquid poolings of thecoating solution CL occur in symmetrical manners on the surfaces of theoptical members 21 a and 21 a and the base material JP of the centralmember 50, to collectively eliminate, at the pair of optical members 21a and 21 b, a deterioration such as whitening or uneven thicknesses ofthe hard coat layers 27 a and 27 b, and to thus manufacture the hardcoat layers 27 a and 27 b being defect-free at a high yield.

In the method for manufacturing the light-guiding device of the firstembodiment, separate overcoat layers 27 a and 27 b are formed at theoptical member 21 a on one side and the optical member 21 b on the otherside relative to the approximate center of the central member 50, tomanufacture the overcoat layers 27 a and 27 b of the pair of opticalmembers 21 a and 21 b in symmetrical processes, and to collectivelyeliminate, at the pair of optical members 21 a and 21 b, a deteriorationsuch as whitening or uneven thicknesses of the hard coat layers 27 a and27 b.

Second Embodiment

Hereinafter, a light-guiding device and a virtual image displayapparatus according to the second embodiment will be described belowwith reference to FIG. 10. Note that the light-guiding device and thevirtual image display apparatus according to the second embodiment arepartially modified from the light-guiding device and the like accordingto the first embodiment, and descriptions on the common parts areomitted.

In case of the light-guiding device 20 illustrated in the figure, asurface scattering layer 61 is provided as a light-guide blockingstructure 72, on a front surface 55 a, the lower surface 50 q, and thelike, in the exposed region AE devoid of the overcoat layer 27 (see FIG.6) provided at the bridge portion 50 z in the central member 50. Thesurface scattering layer 61, which is a diffusion surface including afine concavo-convex structure that scatters image light, can be formedby surface texturing, for example. The surface texturing can beconducted by transferring with a mold when molding is performed. Aprovision of the surface scattering layer 61 in a manner partiallycovering the surface of the central member 50 allows image light to bescattered and dimmed at the time when the image light passes through thecoupling portion 50 d. That is, the image light passing through thecentral member 50 from one of the optical members 21 a and 21 b to theother can be reduced, and thus the image light contributing to formingof a ghosting can be reduced. Note that the arrangement and size of thesurface scattering layer 61 illustrated in FIG. 10 are given as mereexamples, and can be appropriately modified depending on thespecifications of the light-guiding device 20.

A provision of the surface scattering layer 61 in the exposed region AEcan prevent a reduction of scattering efficiency due to the coverage ofthe surface scattering layer 61 by the overcoat layer 27.

Third Embodiment

Hereinafter, a light-guiding device and a virtual image displayapparatus according to the third embodiment will be described below withreference to FIG. 11. Note that the light-guiding device and the virtualimage display apparatus according to the third embodiment are partiallymodified from the light-guiding device and the like according to thefirst embodiment, and descriptions on the common parts are omitted.

In case of the light-guiding device 20 illustrated in the figure, asurface absorption layer 62 is provided as the light-guide blockingstructure 72, on the surfaces such as the front surface 55 a, the lowersurface 50 q, and the like, in the exposed region AE devoid of theovercoat layer 27 (see FIG. 6) provided at the bridge portion 50 z inthe central member 50. The surface absorption layer 62 is a colored partthat absorbs image light. A provision of the surface scattering layer 61in a manner partially covering the surface of the central member 50allows the image light to be scattered and dimmed at the time when theimage light passes through the coupling portion 50 d. That is, the imagelight passing through the central member 50 from one of the opticalmembers 21 a and 21 b to the other can be reduced, and thus the imagelight contributing to forming of a ghosting can be reduced. Note thatthe arrangement and size of the surface absorption layer 62 illustratedin FIG. 11 are given as mere examples, and can be appropriately modifieddepending on the specifications of the light-guiding device 20.

The surface absorption layer 62 is formed by applying and drying alight-absorbing coating material. Specifically, the surface absorptionlayer 62 is formed by an application of a light-blocking coatingmaterial, black-painting, or the like. A provision of the surfaceabsorption layer 62 in the exposed region AE can prevent an applicationprocess of the surface absorption layer 62 from being hindered by theovercoat layer 27 formed in the preceding processes.

The surface absorption layer 62 is not required to completely blockvisible light passing through the coupling portion 50 d. The surfaceabsorption layer 62 is colored in black opaque in specific examples, butmay be one, like ND filter, having semi-transparent properties as longas uniformly absorbing the light in the respective wavelength ranges, ormay have biased characteristics that readily transmit light of somewavelengths.

Fourth Embodiment

Hereinafter, a light-guiding device and a virtual image displayapparatus according to the fourth embodiment will be described belowwith reference to FIGS. 12 and 13. Note that the light-guiding deviceand the virtual image display apparatus according to the fourthembodiment are partially modified from the light-guiding device and thelike according to the first embodiment, and descriptions on the commonparts are omitted.

In case of the light-guiding device 20 illustrated in FIG. 12, the firstovercoat layer 27 a and the second overcoat layer 27 b corresponding tothe right and left at the center portion (the lateral middle portion 50j) of the central member 50 are overlapped to form an overlapped portionAO in a strip shape. Both the overcoat layers 27 a and 27 b areoverlapped to facilitate controlling of the immersion depth and thelike, making it easy to fabricate both the overcoat layers 27 a and 27b, and further enabling an overcoat to protect the entirety of thecentral member 50. Here, a lateral width w1 of the overlapped portion AOis narrower than a lateral width w2 of the positioning structure 71, andthe positioning locations 71 a of the positioning structure 71 arelocated outside of the overlapped portion AO. That is, the pair ofovercoat layers 27 a and 27 b are in a state of individually coveringthe positioning locations 71 a. As a result, the overlapped portion AOis provided in a manner to avoid the positioning locations 71 a of thepositioning structure 71. In this case, the positioning locations 71 aare covered by the overcoat layers 27 a and 27 b, however, if thethicknesses of both the overcoat layers 27 a and 27 b are approximatelyequal to each other and thin, positioning accuracies of the center cover100D and the other components can be prevented from being lowered. Thefirst overcoat layer 27 a and the second overcoat layer 27 b may becomposed of an identical material or composition, as well as may becomposed of different materials or compositions. Even if the firstovercoat layer 27 a and the second overcoat layer 27 b are composed ofan identical material, both the overcoat layers 27 a and 27 b, whenseparately provided, are separate overcoat layers. Even if both theovercoat layers 27 a and 27 b are composed of an identical material, forexample, a composition distribution biased along the thickness directionis formed in many cases within the overcoat layers 27 a and 27 b, wherein these cases, a boundary face having a slight composition transitionis formed between both the overcoat layers 27 a and 27 b.

FIG. 13 is an explanatory graph illustrating thickness of the overcoatlayers 27 a and 27 b at and around the overlapped portion AO. Thehorizontal axis p indicates the positions in the X direction, and thevertical axis t indicates the thicknesses of the overcoat layers 27 aand 27 b. Here, the region indicated by the fine dot pattern indicatesthe thickness of the overcoat layer 27 b formed at the rear side. Theovercoat layers 27 a and 27 b being actual layers, particularly theovercoat layer 27 b at the upper side, has a tendency of becomingnon-uniform in thickness due to the water repelling effect. As apparentfrom the figure as well, at the overlapped portion AO at the center, theovercoat layers 27 a and 27 b are overlapped and the coating thicknessat the overlapped portion AO is relatively thicker than the coatingthickness in single layer regions Ma and Mb outside of the overlappedportion AO. Moreover, the thicknesses are non-uniform in the overlappedportion AO, however, in the single layer regions Ma and Mb outside ofthe overlapped portion AO, the overcoat layers 27 a and 27 b areindividually formed and the thicknesses are substantially equal to eachother. That is, the overcoat layers 27 a and 27 b individually formedare to cover the respective positioning locations 71 a, to eliminate theinfluence on the positioning accuracies.

Fifth Embodiment

Hereinafter, a light-guiding device and a virtual image displayapparatus according to the fifth embodiment will be described below withreference to FIG. 14. Note that the light-guiding device and the virtualimage display apparatus according to the fifth embodiment are partiallymodified from the light-guiding device and the like according to thefirst and fourth embodiments, and descriptions on the common parts areomitted.

In case of the light-guiding device 20 illustrated in FIG. 14, a coloredportion 54 composed of colored resin is provided at the bridge portion50 z in the central member 50. The colored portion 54 is provided in amanner traversing the bridge portion 50 z, and is provided in a mannertraversing the central member 50 in relation to a plane being parallelto the YZ plane. The colored portion 54 includes the light-guideblocking structure 72, and has light absorption properties for visiblelight. The colored portion 54 absorbs and attenuates the image lightbeing incident on the colored portion 54. That is, the image lightpassing through the central member 50 from one of the optical members 21a and 21 b to the other can be reduced, and the image light contributingto forming of a ghosting can be reduced. Note that the arrangement andsize of the colored portion 54 illustrated in FIG. 14 are given as mereexamples, and can be appropriately modified depending on thespecifications of the light-guiding device 20. The colored portion 54can be formed in the exposed region AE, without being limited to theoverlapped portion AO.

A method of fabricating the central member 50 including the bridgeportion 50 z embedded with the colored portion 54 will be describedbelow. The central member 50 is formed using injection molding method,which is referred to as two-color molding, for example. Specifically, amold including a mold space corresponding to the colored portion 54 isprepared, and then a thermoplastic resin having light absorptionproperties is injected into this mold space, to be solidified to formthe colored portion 54. Thereafter, metallic mold spaces correspondingto the light transmissive portions 50 a and 50 b and the like areexpanded, then a thermoplastic resin having light transmissivity isinjected into this expanded spaces, to thus individually form a portionincluding the light transmissive portion 50 a and a portion at thebridge portion 50 z side of the light transmissive portion 50 a, and aportion including the light transmissive portion 50 b and a portion atthe bridge portion 50 z side of the light transmissive portion 50 b.Then, transition portions 56 a and 56 b are fused to the colored portion54 to be firmly joined to the colored portion 54, to complete thecentral member 50. That is, the central member 50 integrated with thelight-guide blocking structure 72 can be collectively fabricated. Theresin material of the colored portion 54 is prepared from a resinmaterial of the same type as that of the light transmissive portions 50a and 50 b and a black dye added thereto, under molding conditionshaving difference in increased glass transition temperature and the likecompared to the resin material of the light transmissive portions 50 aand 50 b.

The colored portion 54 is not required to completely block visible lightpassing through the coupling portion 50 d. The colored portion 54 iscolored in black opaque in specific examples, but may be one, like NDfilter, having semi-transparent properties as long as uniformlyabsorbing the light in the respective wavelength ranges, or may havebiased characteristics that readily transmit light of some wavelengths.

As in the modification illustrated in FIG. 15, a colored portion 154being layered may also be formed to traverse the bridge portion 50 z inthe central member 50. The colored portion 154 can be embedded withinthe bridge portion 50 z using film insert molding method or sheet insertmolding method. Specifically, a light absorbing film is fixed inside amold, and a thermoplastic resin having light transmissivity is injectedinto both of mold spaces partitioned by a light absorbing film to besolidified, to thus complete the central member 50 including the bridgeportion 50 z or the coupling portion 50 d. Note that the arrangement andthe like of the colored portion 154 illustrated in FIG. 15 are given asmere examples, and can be appropriately modified depending on thespecifications of the light-guiding device 20, where the arrangement mayalso be separated at a plurality of locations, without being limited toa single location, to form a colored portion. The colored portion 154can be formed in the exposed region AE, without being limited to theoverlapped portion AO.

Sixth Embodiment

Hereinafter, a light-guiding device and a virtual image displayapparatus according to the sixth embodiment will be described below withreference to FIG. 16. Note that the light-guiding device and the virtualimage display apparatus according to the sixth embodiment are partiallymodified from the light-guiding device and the like according to thefirst and fourth embodiments, and descriptions on the common parts areomitted.

In case of the light-guiding device 20 illustrated in the figure, asurface absorption layer 162 is provided as the light-guide blockingstructure 72, on the surfaces such as the front surface 55 a, the lowersurface 50 q, and the like, at the bridge portion 50 z in the centralmember 50. The surface absorption layer 162 is a layered colored portionthat absorbs image light, and is integrated with a base material of thebridge portion 50 z. The surface absorption layer (colored portion) 162can be a surface layer integrated with the central member 50, using asheet insert molding method, for example. Note that the arrangement andsize of the colored portion 54 illustrated in FIG. 16 are given as mereexamples, and can be appropriately modified depending on thespecifications of the light-guiding device 20, where the arrangement mayalso be separated at a plurality of locations, without being limited toa single location, to form a colored portion. The surface absorptionlayer 162 can be formed in the exposed region AE, without being limitedto the exposed region AE.

Seventh Embodiment

Hereinafter, a light-guiding device and a virtual image displayapparatus according to the seventh embodiment will be described belowwith reference to FIGS. 17 and 18. Note that the light-guiding deviceand the virtual image display apparatus according to the seventhembodiment are partially modified from the light-guiding device and thelike according to the first embodiment, and descriptions on the commonparts are omitted.

In case of the light-guiding device 20 illustrated in FIG. 17, thecoupling portion 50 d is devoid of the bridge portion 50 z (see FIG. 5A)in the central member 50.

In case of the light-guiding device 20 illustrated in FIG. 18, only thenotch 57 is provided at the coupling portion 50 d of the central member50 to omit the protrusion portion 58. Note that, although notillustrated in the figure, only the protrusion portion 58 may also beprovided at the coupling portion 50 d to omit the notch 57.

Modifications and Other Particulars

In the first and fourth embodiments and the like described above, thebase material JP is pulled up with being held substantiallyperpendicular to the coating solution, however, the base material JP mayalso be pulled up with being disposed at a large inclination relative tothe coating solution CL. In this case, for example, the base material JPcan be pulled up with height positions of the outward steps SA1 and SA2from the coating solutions CL coinciding with each other, and the speedsat which the outward steps A1 and SA2 pass through the liquid surfacecan be reduced. This allows the pulling-up speed at the steps to bereduced, and the coating film CF of the coating solution CL to bethinner. In this case, an occurrence of liquid pooling is suppressedeven if the steps are oriented inward.

In the embodiments described above, the coupling portion 50 d of thecentral member 50 is shifted upward relative to the optical members 21 aand 21 b, however, the coupling portion 50 d may be shifted toward thediagonally upper front side or the −Y+Z direction relative to theoptical members 21 a and 21 b.

The central member 50 is sufficient to have light transmissivity in thepair of light transmissive portions 50 a and 50 b, and the entirety ofthe coupling portion 50 d may be formed from a material devoid of lighttransmissivity.

The half mirror 15 may also be constituted by a volume hologram or theother hologram element, or may also be constituted by a diffractiongrating.

In the virtual image display apparatus 100 in the above-describedembodiments, a self-luminous display element such as an organic ELelement is used as the image forming device 80. Instead, a configurationin which a laser scanner is configured by combining a laser light sourcewith a scanner, such as a polygon mirror, may also be used as the imageforming device 80.

In a specific aspect of the present disclosure, a first overcoat layerand a second overcoat layer corresponding to separate overcoat layersare spaced apart from each other at a center portion of a centralmember. In this case, a region where the base material is exposed can beformed at the center portion of the central member, to increase thedegree of freedom of the subsequent processings.

In another specific aspect of the present disclosure, a positioningstructure is provided at the center portion of the central member, andthe first overcoat layer and the second overcoat layer are provided in amanner to avoid a positioning location of the positioning structure. Inthis case, finishing accuracy of the positioning location can bemaintained in a simple manner.

In another specific aspect of the present disclosure, a surfacescattering layer or a surface absorption layer is provided, at a surfaceof the central member, at a location where the first overcoat layer andthe second overcoat layer are spaced apart from each other. This allowsa light-guide blocking structure that suppresses an occurrence of ghostlight to be incorporated.

In a specific aspect of the present disclosure, a first overcoat layerand a second overcoat layer corresponding to separate overcoat layersoverlap at a center portion of the central member. In this case, theentirety of the central member can be protected by an overcoat.

In another specific aspect of the present disclosure, a coatingthickness is relatively thick at a location where the first overcoatlayer and the second overcoat layer overlap.

In another specific aspect of the present disclosure, a positioningstructure is provided at a center portion of the central member, and anoverlapped portion having a relatively large coating thickness due to anoverlap between the first overcoat layer and the second overcoat layeris provided in a manner to avoid a positioning location of thepositioning structure. In this case, the positioning location is coveredby the first and second overcoat layers, and if the thicknesses of boththe overcoat layers are approximately equal to each other and thin,positioning accuracies of the other components relative to thepositioning structure can be prevented from being lowered.

In another specific aspect of the present disclosure, the overlappedportion has a lateral width narrower than a lateral width of thepositioning structure. In this case, an arrangement in which overlappedportions avoid the positioning locations can be achieved in a simplemanner.

In another specific aspect of the present disclosure, a colored portionformed by two-color molding is provided at an approximate center of thecentral member. This allows a light-guide blocking structure thatsuppresses an occurrence of ghost light to be incorporated. Then, thecentral member integrated with the light-guide blocking structure can becollectively fabricated.

In another specific aspect of the present disclosure, a colored portionis formed by sheet insert molding at an approximate center of thecentral member. This allows a light-guide blocking structure thatsuppresses an occurrence of ghost light to be incorporated. Then, thecentral member integrated with the light-guide blocking structure can becollectively fabricated.

In another specific aspect of the disclosure, a pair of optical membersinclude outward steps provided in a concave shape at a tip end side awayfrom the central member. At the time when a base material to which anoptical member and a central member are joined is pulled up with a tipend side being oriented to a lower side, the outward step is in anoverhanging state, suppressing an occurrence of a liquid pooling ofcoating solution.

In another specific aspect of the disclosure, a pair of optical membersinclude outward steps at a front side and a back side. In this case,coating defects can be suppressed from occurring at the front and backoutward steps.

In another specific aspect of the disclosure, a light-guiding device isthe light-guiding device including a first optical member, a secondoptical member, and a central member having light transmissivity, inwhich the first optical member includes a first light-guiding portion, afirst light-incident portion configured to cause image light to beincident on the first light-guiding portion, and a first light-emittingportion configured to cause the image light guided by the firstlight-guiding portion to exit outside, in which the second opticalmember includes a second light-guiding portion, a second light-incidentportion configured to cause image light to be incident on the secondlight-guiding portion, and a second light-emitting portion configured tocause the image light guided by the second light-guiding portion to exitoutside, in which the first optical member and the second optical memberare coupled by the central member (having light transmissivity), and inwhich a first overcoat layer and a second overcoat layer are separatelyprovided at the optical member on one side and at the optical member onanother side relative to an approximate center of the central member.

In another specific aspect of the present disclosure, a virtual imagedisplay apparatus includes the above-described light-guiding device, andan image forming body configured to form image light that is to beguided to the light-guiding device, and guides image light reflected bya pair of half mirrors provided between a pair of optical members andthe central member.

A method for manufacturing a light-guiding device according to an aspectof the present disclosure is the method for manufacturing alight-guiding device including a pair of light-guiding portions, a pairof light-incident portions configured to cause image light to beincident on the pair of light-guiding portions respectively, and a pairof light-emitting portions configured to emit image light, guided bythee pair of light-guiding portions, to outside respectively, in whichseparate overcoat layers are formed at an optical member on one side andat an optical member on another side relative to an approximate centerof the central member.

What is claimed is:
 1. A light-guiding device comprising: a pair oflight-guiding portions; a pair of light-incident portions configured tocause image light to be incident on the pair of light-guiding portionsrespectively; and a pair of light-emitting portions configured to emitimage light, guided by the pair of light-guiding portions, to outsiderespectively, wherein a pair of optical members including the pair oflight-guiding portions are coupled by a central member, and separateovercoat layers are provided at the optical member on one side and atthe optical member on another side with respect to an approximate centerof the central member.
 2. The light-guiding device according to claim 1,wherein a first overcoat layer and a second overcoat layer correspondingto the separate overcoat layers are spaced apart from each other at acenter portion of the central member.
 3. The light-guiding deviceaccording to claim 2, wherein a positioning structure is provided at thecenter portion of the central member, and the first overcoat layer andthe second overcoat layer are formed in a manner to avoid a positioninglocation of the positioning structure.
 4. The light-guiding deviceaccording to claim 2, wherein a surface scattering layer or a surfaceabsorption layer is formed, at a surface of the central member, at alocation where the first overcoat layer and the second overcoat layerare spaced apart from each other.
 5. The light-guiding device accordingto claim 1, wherein a first overcoat layer and a second overcoat layercorresponding to the separate overcoat layers overlap at a centerportion of the central member.
 6. The light-guiding device according toclaim 5, wherein a coating thickness is relatively thick at a locationwhere the first overcoat layer and the second overcoat layer overlap. 7.The light-guiding device according to claim 6, wherein a positioningstructure is provided at the center portion of the central member, andan overlapped portion having a relatively large coating thickness due tothe overlap between the first overcoat layer and the second overcoatlayer is formed in a manner to avoid a positioning location of thepositioning structure.
 8. The light-guiding device according to claim 7,wherein the overlapped portion has a lateral width narrower than alateral width of the positioning structure.
 9. The light-guiding deviceaccording to claim 5, wherein a colored portion formed by two-colormolding is formed at an approximate center of the central member. 10.The light-guiding device according to claim 5, wherein a colored portionis formed by sheet insert molding at the approximate center of thecentral member.
 11. The light-guiding device according to claim 1,wherein the pair of optical members include an outward step provided ina concave shape at a tip end side away from the central member.
 12. Thelight-guiding device according to claim 11, wherein the pair of opticalmembers include the outward step at a front side and a back side.
 13. Alight-guiding device comprising: a first optical member; a secondoptical member; and a central member having light transmissivity,wherein the first optical member includes a first light-guiding portion,a first light-incident portion configured to cause image light to beincident on the first light-guiding portion, and a first light-emittingportion configured to emit the image light, guided by the firstlight-guiding portion, to outside, wherein the second optical memberincludes a second light-guiding portion, a second light-incident portionconfigured to cause image light to be incident on the secondlight-guiding portion, and a second light-emitting portion configured toemit the image light, guided by the second light-guiding portion, tooutside, wherein the first optical member and the second optical memberare coupled by the central member, and a first overcoat layer and asecond overcoat layer are separately provided at the optical member onone side and at the optical member on another side with respect to anapproximate center of the central member.
 14. A virtual image displayapparatus comprising: a light-guiding device according to claim 1; andan image forming body configured to form image light that is to beguided to the light-guiding device, and guiding image light, reflectedby a pair of half mirrors formed between the pair of optical members andthe central member, to an exit pupil.
 15. A method for manufacturing alight-guiding device including a pair of light-guiding portions, a pairof light-incident portions configured to cause image light to beincident on the pair of light-guiding portions respectively, and a pairof light-emitting portions configured to emit image light, guided by thepair of light-guiding portions, to outside respectively, whereinseparate overcoat layers are formed at an optical member on one side andat an optical member on another side with respect to an approximatecenter of a central member.
 16. The method for manufacturing alight-guiding device according to claim 15, wherein a first overcoatlayer and a second overcoat layer corresponding to the separate overcoatlayers are spaced apart from each other at a center portion of thecentral member.
 17. The method for manufacturing a light-guiding deviceaccording to claim 16, wherein a positioning structure is formed at thecenter portion of the central member, and the first overcoat layer andthe second overcoat layer are formed in a manner to avoid thepositioning structure.
 18. The method for manufacturing a light-guidingdevice according to claim 15, wherein a first overcoat layer and asecond overcoat layer corresponding to the separate overcoat layersoverlap at a center portion of the central member.
 19. The method formanufacturing a light-guiding device according to claim 18, wherein apositioning structure is formed at the center portion of the centralmember, and the first overcoat layer and the second overcoat layer areformed in such a way that an overlapped portion between the firstovercoat layer and the second overcoat layer avoids a positioninglocation of the positioning structure.